Nixpanic's Blog

A minor annoyance on with wireless networking at home seems to easily resolved. I'm very happy that NetworkManager offers a CLI that works together with the GNOME-NetworkManager-applet. cnetworkmanager does, or at least did not work for me.

The WiFi at home uses a hidden ESSID and it looks like NetworkManager does not connect to this automatically. Well, that's not completely correct, it just takes a lot of time for NetworkManager to attempt to connect. It's unclear to me why NetworkManager sometimes connect me automatically, and sometimes it seems to take ages and manually connecting to the hidden wireless network is quicker.

This little script ~/bin/nm-connect-me.sh forces NetworkManager to connect to the hidden WiFi when wireless is enabled and there is no connection yet:
#!/bin/sh
#
# Automatically try to connect to 'MyWiFi' when WiFi is enabled
#

# the output of nmcli should be in English
LC_ALL=C

# loop for a while until NetworkManager is accepting commands
while [ "$(nmcli -t -f WIFI,STATE nm)" = 'enabled:disconnected' ]
do
nmcli con up id MyWiFi
sleep 5
done

exit 0

After making the script executable and adding it as a startup application over xfce4-session-settings, the network connection is established immediately when I login. It really bids me a little more comfort when turning on my laptop.

The changelog from the NetworkManager package shows that nmcli was added about one year ago! Such a shame that I only found out about it recently...

This is a short explanation on how to create a bootable USB-stick with GRUB. This stick can be used to boot an installer, rescue-mode or an on-stick installed Linux distribution.

I mainly use my USB-stick to install different versions (and architectures) of RHEL. Booting from this USB-stick and starting and starting a kickstart installation is really convenient.

Detect the USB-stick

This is a very important step and the one where most attention is needed. Detecting the device-node where the USB-stick is connected should not go wrong. Picking the wrong drive will not make your system unbootable (as we're creating a bootable disk), but all data will be lost!

To detect which device-node is used for the USB-stick, I tend to check the output from the command 'dmesg'. This commmand displays the contents of the kernel-log-buffer and the last lines contain the last events. Insert the USB-stick and shortly after that checking 'dmesg', results for me in the following output (truncated here, only the last importan messages are shown):
usb 1-2: new high speed USB device using ehci_hcd and address 5
usb 1-2: New USB device found, idVendor=1e3d, idProduct=2093
usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 1-2: Product:
usb 1-2: Manufacturer: USB 2.0
usb 1-2: SerialNumber: 26073604A307E205
usb 1-2: configuration #1 chosen from 1 choice
scsi4 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 5
usb-storage: waiting for device to settle before scanning
usb-storage: device scan complete
scsi 4:0:0:0: Direct-Access USB 2.0 5.00 PQ: 0 ANSI: 2
sd 4:0:0:0: Attached scsi generic sg2 type 0
sd 4:0:0:0: [sdc] 4067328 512-byte logical blocks: (2.08 GB/1.93 GiB)
sd 4:0:0:0: [sdc] Write Protect is off
sd 4:0:0:0: [sdc] Mode Sense: 0b 00 00 08
sd 4:0:0:0: [sdc] Assuming drive cache: write through
sd 4:0:0:0: [sdc] Assuming drive cache: write through
sdc: sdc1 sdc2
The USB-stick just connected is called 'sdc' and obviously contiains two partitions: sdc1 and sdc2. The matching device-node for this USB-stick is '/dev/sdc'.

Prtitioning the USB-stick

There exist a lot of tools to perform partitioning of a disk. One of the most common tools is 'fdisk' and that is very esy to use, therefore I mostly use this tool too.

'fdisk' takes the device-node as parameter, starting 'fdisk' looks like this:
# fdisk /dev/sdc

The number of cylinders for this disk is set to 32280.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)

Command (m for help):
In order to make the USB-stick usable on a lot of systems, it seems to be a good idea to create a MSDOS-partitiontable on it.
Command (m for help): o
Building a new DOS disklabel with disk identifier 0x077c807a.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.

The number of cylinders for this disk is set to 32280.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
The only purpose of this stick will be that it is able to boot a range of kernels. Using it to save or transfer files is not important and therefore this stick will contain one VFAT partition. This makes it possible to add files and change the configuration under practically any operating system.

Create one primary partition:
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
The partition should be the first partition:
Partition number (1-4): 1
The start of the partition should be the first cylinder on the disk:
First cylinder (1-32280, default 1):
Using default value 1
By default the size of the partition will be the whole disk:
Last cylinder, +cylinders or +size{K,M,G} (1-32280, default 32280):
Using default value 32280
Change the type of the partition:
Command (m for help): t
Selected partition 1
VFAT is most portable, so choose 'c' (the hex-value for VFAT):
Hex code (type L to list codes): c
Changed system type of partition 1 to c (W95 FAT32 (LBA))
Mark the newly created partition bootable (probably not needed though):
Command (m for help): a
Partition number (1-4): 1
Check if all has been configured correctly, nothing has been saved yet:
Command (m for help): p

Disk /dev/sdc: 2082 MB, 2082471936 bytes
2 heads, 63 sectors/track, 32280 cylinders
Units = cylinders of 126 * 512 = 64512 bytes
Disk identifier: 0x077c807a

Device Boot Start End Blocks Id System
/dev/sdc1 * 1 32280 2033608+ c W95 FAT32 (LBA)
If all looks okay, write the changes to the partitiontable on the disk:
Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
After this, the kernel got instructed to read the new partitiontable. The result should be that there is a new /dev/sdc1. Before this new partition can be used, it should be formatted:
# mkfs -t vfat -n ndevos /dev/sdc1
With the new filesystem on the USB-stick, it is now possible to mount the stick:
# mount /dev/sdc1 /mnt
and copy the required files for the bootloader:
# mkdir -p /mnt/boot/grub
# cp /boot/grub/* /mnt/boot/grub/
Before the bootlaoder can get installed in the Master Boot Record (MBR), it needs to get mapped, so that GRUB recognises the USB-stick as first bootable disk. This can be done by changing the device.map file (or creating it if missing):
[root@localhost ~]# cat /mnt/boot/grub/device.map
# this device map was generated by ndevos on eeepc
(hd0) /dev/sdc
This example shows that (hd0) is mapped to /dev/sdc.

Installing GRUB with the updated device.map file is done like this:
# grub --device-map=/mnt/boot/grub/device.map


GNU GRUB version 0.97 (640K lower / 3072K upper memory)

[ Minimal BASH-like line editing is supported. For the first word, TAB
lists possible command completions. Anywhere else TAB lists the possible
completions of a device/filename.]
grub> root (hd0,0)
root (hd0,0)
Filesystem type is fat, partition type 0xc
grub> setup (hd0)
setup (hd0)
Checking if "/boot/grub/stage1" exists... yes
Checking if "/boot/grub/stage2" exists... yes
Checking if "/boot/grub/fat_stage1_5" exists... yes
Running "embed /boot/grub/fat_stage1_5 (hd0)"... 27 sectors are embedded.
succeeded
Running "install /boot/grub/stage1 (hd0) (hd0)1+27 p (hd0,0)/boot/grub/stage2 /boot/grub/grub.conf"... succeeded
Done.
grub> quit
quit
The USB-stick does now contain a working GRUB and can be used to bootstrap an installer (or rescue disk) for any Fedora, RHEL and possibly other Linux distributions. The only two things that needs to be done before this works are

1. copy the vmlinz and initrd.img to the /mnt/boot directory
2. update the /mnt/boot/grub/grub.conf with lines to boot the new kernel (with any options you like) with the matching initrd

To enable access to a (virtual) system over a serial console I'm doing following steps:

1) add a login-prompt on the serial console

echo 'S0:2345:respawn:/sbin/agetty ttyS0 115200 vt100' >> /etc/inittab

2) allow root to login over serial console

echo ttyS0 >> /etc/securetty

3) let /sbin/init reload the inittab to make the login prompt active

/sbin/telinit q

Now you can connect to the serial console and after pressing 'return' you should see a login prompt.

Optionally put the output of the kernel and boot process over the console
4) add parameters console=tty0 console=ttyS0,115200 to the kernel line in /boot/grub/grub.conf

title Red Hat Enterprise Linux AS (2.6.9-78.EL)
 root (hd0,0)
  kernel /vmlinuz-2.6.9-78.EL ro root=/dev/VolGroup00/LogVol00 console=tty0 console=ttyS0,115200
  initrd /initrd-2.6.9-78.EL.img

By adding both parameters console=tty0 and console=ttyS0,115200, the output of the kernel is sent to both consoles. For the boot messages the last console is used. This is useful if your main console is a serial one, but you also have a real (or virtual) monitor connected.

This is what I see when booting one of my virtual systems on Fedora 11:

# virsh start --console rhel4
Domain rhel4 started
Connected to domain rhel4
Escape character is ^]
Linux version 2.6.9-78.EL (brewbuilder@hs20-bc2-3.build.redhat.com) (gcc version 3.4.6 20060404 (Red Hat 3.4.6-10)) #1 Wed Jul 9 15:27:01 EDT 2008
BIOS-provided physical RAM map:
BIOS-e820: 0000000000000000 - 000000000009f000 (usable)
BIOS-e820: 000000000009f000 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000e8000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 000000001fff0000 (usable)
BIOS-e820: 000000001fff0000 - 0000000020000000 (ACPI data)
BIOS-e820: 00000000fffbc000 - 0000000100000000 (reserved)
0MB HIGHMEM available.
511MB LOWMEM available.
found SMP MP-table at 000fbd10
Using x86 segment limits to approximate NX protection
zapping low mappings.
DMI 2.4 present.
ACPI: PM-Timer IO Port: 0xb008
ACPI: LAPIC (acpi_id[0x00] lapic_id[0x00] enabled)
Processor #0 6:3 APIC version 20
ACPI: LAPIC (acpi_id[0x01] lapic_id[0x01] disabled)
ACPI: LAPIC (acpi_id[0x02] lapic_id[0x02] disabled)
ACPI: LAPIC (acpi_id[0x03] lapic_id[0x03] disabled)
ACPI: LAPIC (acpi_id[0x04] lapic_id[0x04] disabled)
ACPI: LAPIC (acpi_id[0x05] lapic_id[0x05] disabled)
ACPI: LAPIC (acpi_id[0x06] lapic_id[0x06] disabled)
ACPI: LAPIC (acpi_id[0x07] lapic_id[0x07] disabled)
ACPI: LAPIC (acpi_id[0x08] lapic_id[0x08] disabled)
ACPI: LAPIC (acpi_id[0x09] lapic_id[0x09] disabled)
ACPI: LAPIC (acpi_id[0x0a] lapic_id[0x0a] disabled)
ACPI: LAPIC (acpi_id[0x0b] lapic_id[0x0b] disabled)
ACPI: LAPIC (acpi_id[0x0c] lapic_id[0x0c] disabled)
ACPI: LAPIC (acpi_id[0x0d] lapic_id[0x0d] disabled)
ACPI: LAPIC (acpi_id[0x0e] lapic_id[0x0e] disabled)
ACPI: LAPIC (acpi_id[0x0f] lapic_id[0x0f] disabled)
Enabling APIC mode: Flat. Using 0 I/O APICs
ACPI: IOAPIC (id[0x01] address[0xfec00000] gsi_base[0])
IOAPIC[0]: apic_id 1, version 17, address 0xfec00000, GSI 0-23
ACPI: INT_SRC_OVR (bus 0 bus_irq 5 global_irq 5 high level)
ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 high level)
ACPI: INT_SRC_OVR (bus 0 bus_irq 10 global_irq 10 high level)
ACPI: INT_SRC_OVR (bus 0 bus_irq 11 global_irq 11 high level)
Using ACPI (MADT) for SMP configuration information
Allocating PCI resources starting at 30000000 (gap: 20000000:dffbc000)
Built 1 zonelists
Kernel command line: ro root=/dev/VolGroup00/LogVol00 console=tty0 console=ttyS0,115200 elevator=noop
Initializing CPU#0
CPU 0 irqstacks, hard=c0418000 soft=c0417000
PID hash table entries: 2048 (order: 11, 32768 bytes)
Detected 2394.771 MHz processor.
Using pmtmr for high-res timesource
Console: colour VGA+ 80x25
Dentry cache hash table entries: 131072 (order: 7, 524288 bytes)
Inode-cache hash table entries: 65536 (order: 6, 262144 bytes)
Memory: 513840k/524224k available (2209k kernel code, 9752k reserved, 745k data, 172k init, 0k highmem)
Calibrating delay using timer specific routine.. 4560.74 BogoMIPS (lpj=2280372)
Security Scaffold v1.0.0 initialized
SELinux: Initializing.
selinux_register_security: Registering secondary module capability
Capability LSM initialized as secondary
Mount-cache hash table entries: 512 (order: 0, 4096 bytes)
CPU: L1 I cache: 32K, L1 D cache: 32K
CPU: L2 cache: 2048K
CPU: Intel Pentium II (Klamath) stepping 03
Enabling fast FPU save and restore... done.
Enabling unmasked SIMD FPU exception support... done.
Checking 'hlt' instruction... OK.
ENABLING IO-APIC IRQs
..TIMER: vector=0x31 pin1=0 pin2=-1
checking if image is initramfs... it is
Freeing initrd memory: 1175k freed
NET: Registered protocol family 16
PCI: PCI BIOS revision 2.10 entry at 0xfb510, last bus=0
PCI: Using configuration type 1
mtrr: v2.0 (20020519)
ACPI: Subsystem revision 20040816
ACPI: Interpreter enabled
ACPI: Using IOAPIC for interrupt routing
ACPI: PCI Root Bridge [PCI0] (00:00)
PCI: Probing PCI hardware (bus 00)
ACPI: PCI Interrupt Link [LNKA] (IRQs 5 *10 11)
ACPI: PCI Interrupt Link [LNKB] (IRQs 5 *10 11)
ACPI: PCI Interrupt Link [LNKC] (IRQs 5 10 *11)
ACPI: PCI Interrupt Link [LNKD] (IRQs 5 10 *11)
Linux Plug and Play Support v0.97 (c) Adam Belay
xen_mem: Initialising balloon driver.
usbcore: registered new driver usbfs
usbcore: registered new driver hub
PCI: Using ACPI for IRQ routing
ACPI: PCI Interrupt Link [LNKD] enabled at IRQ 11
ACPI: PCI Interrupt 0000:00:01.2[D] -> GSI 11 (level, high) -> IRQ 11
ACPI: PCI Interrupt Link [LNKA] enabled at IRQ 10
ACPI: PCI Interrupt 0000:00:01.3[A] -> GSI 10 (level, high) -> IRQ 10
ACPI: PCI Interrupt Link [LNKC] enabled at IRQ 11
ACPI: PCI Interrupt 0000:00:03.0[A] -> GSI 11 (level, high) -> IRQ 11
ACPI: PCI Interrupt 0000:00:04.0[A] -> GSI 11 (level, high) -> IRQ 11
ACPI: PCI Interrupt 0000:00:05.0[A] -> GSI 10 (level, high) -> IRQ 10
apm: BIOS version 1.2 Flags 0x03 (Driver version 1.16ac)
apm: overridden by ACPI.
audit: initializing netlink socket (disabled)
audit(1247389170.873:1): initialized
Total HugeTLB memory allocated, 0
VFS: Disk quotas dquot_6.5.1
Dquot-cache hash table entries: 1024 (order 0, 4096 bytes)
Initializing Cryptographic API
ksign: Installing public key data
Loading keyring
- Added public key 9ADA2B4B1EC241DE
- User ID: Red Hat, Inc. (Kernel Module GPG key)
PCI: PIIX3: Enabling Passive Release on 0000:00:01.0
Limiting direct PCI/PCI transfers.
Activating ISA DMA hang workarounds.
pci_hotplug: PCI Hot Plug PCI Core version: 0.5
ACPI: Processor [CPU0] (supports C1)
Real Time Clock Driver v1.12
Linux agpgart interface v0.100 (c) Dave Jones
serio: i8042 AUX port at 0x60,0x64 irq 12
serio: i8042 KBD port at 0x60,0x64 irq 1
Serial: 8250/16550 driver $Revision: 1.90 $ 68 ports, IRQ sharing enabled
�ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
RAMDISK driver initialized: 16 RAM disks of 16384K size 1024 blocksize
Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2
ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
PIIX3: IDE controller at PCI slot 0000:00:01.1
PIIX3: chipset revision 0
PIIX3: not 100% native mode: will probe irqs later
ide0: BM-DMA at 0xc000-0xc007, BIOS settings: hda:pio, hdb:pio
ide1: BM-DMA at 0xc008-0xc00f, BIOS settings: hdc:pio, hdd:pio
hda: QEMU HARDDISK, ATA DISK drive
Using noop io scheduler
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
hdc: QEMU DVD-ROM, ATAPI CD/DVD-ROM drive
ide1 at 0x170-0x177,0x376 on irq 15
hda: max request size: 1024KiB
hda: 16777216 sectors (8589 MB) w/256KiB Cache, CHS=16383/255/63, (U)DMA
hda: hda1 hda2
hdc: ATAPI 4X CD-ROM drive, 512kB Cache, (U)DMA
Uniform CD-ROM driver Revision: 3.20
ide-floppy driver 0.99.newide
usbcore: registered new driver hiddev
usbcore: registered new driver usbhid
drivers/usb/input/hid-core.c: v2.0:USB HID core driver
mice: PS/2 mouse device common for all mice
input: AT Translated Set 2 keyboard on isa0060/serio0
input: ImExPS/2 Generic Explorer Mouse on isa0060/serio1
md: md driver 0.90.0 MAX_MD_DEVS=256, MD_SB_DISKS=27
NET: Registered protocol family 2
IP route cache hash table entries: 8192 (order: 3, 32768 bytes)
TCP established hash table entries: 32768 (order: 6, 262144 bytes)
TCP bind hash table entries: 32768 (order: 7, 917504 bytes)
TCP: Hash tables configured (established 32768 bind 32768)
Initializing IPsec netlink socket
NET: Registered protocol family 1
NET: Registered protocol family 17
ACPI wakeup devices:

ACPI: (supports S3 S4 S5)
Freeing unused kernel memory: 172k freed
Red Hat nash version 4.2.1.13 starting
Mounted /proc filesystem
Mounting sysfs
Creating /dev
Starting udev
Loading dm-mod.ko module
device-mapper: 4.5.5-ioctl (2006-12-01) initialised: dm-devel@redhat.com
Loading jbd.ko module
Loading ext3.ko module
Loading dm-mirror.ko module
Loading dm-zero.ko module
Loading dm-snapshot.ko module
Making device-mapper control node
Scanning logical volumes
Reading all physical volumes. This may take a while...
Found volume group "VolGroup00" using metadata type lvm2
Activating logical volumes
2 logical volume(s) in volume group "VolGroup00" now active
Creating root device
Mounting root filesystem
kjournald starting. Commit interval 5 seconds
EXT3-fs: mounted filesystem with ordered data mode.
Switching to new root
INIT: version 2.85 booting
Setting default font (latarcyrheb-sun16): [ OK ]

Welcome to Red Hat Enterprise Linux AS
Press 'I' to enter interactive startup.
Setting clock (utc): Sun Jul 12 09:59:43 BST 2009 [ OK ]
Starting udev: [ OK ]
Initializing hardware... storage network audio done[ OK ]
Configuring kernel parameters: [ OK ]
Loading default keymap (de-latin1): [ OK ]
Setting hostname localhost.localdomain: [ OK ]
Checking root filesystem
[/sbin/fsck.ext3 (1) -- /] fsck.ext3 -a /dev/VolGroup00/LogVol00
/dev/VolGroup00/LogVol00: clean, 64778/897600 files, 397753/1794048 blocks
[ OK ]
Remounting root filesystem in read-write mode: [ OK ]
No RAID disks
Setting up Logical Volume Management: [ OK ]
Checking filesystems
Checking all file systems.
[/sbin/fsck.ext3 (1) -- /boot] fsck.ext3 -a /dev/hda1
/boot: clean, 35/26104 files, 12799/104388 blocks
[ OK ]
Mounting local filesystems: [ OK ]
Enabling local filesystem quotas: [ OK ]
Enabling swap space: [ OK ]
INIT: Entering runlevel: 3
Entering non-interactive startup
Applying Intel Microcode update: [ OK ]
Starting monitoring for VG VolGroup00: [ OK ]
Checking for new hardware [ OK ]
Starting pcmcia: [ OK ]
Setting network parameters: [ OK ]
Bringing up loopback interface: [ OK ]
Bringing up interface eth0: [ OK ]
Bringing up interface eth1:
Determining IP information for eth1... failed.
[FAILED]
Starting system logger: [ OK ]
Starting kernel logger: [ OK ]
Starting portmap: [ OK ]
Starting NFS statd: [ OK ]
Starting RPC idmapd: [ OK ]
Mounting other filesystems: [ OK ]
Starting lm_sensors: [ OK ]
Starting automount: No Mountpoints Defined[ OK ]
Starting smartd: [FAILED]
Starting acpi daemon: [ OK ]
Starting cups: [ OK ]
Starting sshd:[ OK ]
Starting xinetd: [ OK ]
Starting sendmail: [ OK ]
Starting sm-client: [ OK ]
Starting console mouse services: [ OK ]
Starting crond: [ OK ]
Starting xfs: [ OK ]
Starting anacron: [ OK ]
[ OK ] atd: [ OK ]
Starting system message bus: [ OK ]
Starting Red Hat Network Daemon: [ OK ]
Starting HAL daemon: [ OK ]

Red Hat Enterprise Linux AS release 4 (Nahant Update 8)
Kernel 2.6.9-78.EL on an i686

localhost.localdomain login: